JPS6367741A - Hinge tape - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to tape automatic bonding (TAB) of semiconductor devices.
) regarding. Reference is made to US Pat. No. 4,234,666 for the basic teachings of TAB. 19
Co-pending Application No. 138.030, ``Lead Design for Automated Semiconductor Assembly,'' dated April 7, 1980 (Carmen, D., Burns) (currently No. 407,51, dated August 12, 1982)
No. 5 (abandoned for continuation application) discloses a bonding tape having an integral strain relief material useful in thermocompression bonding. The teachings in the above references are incorporated herein by reference.

Basically, in the single layer tape version of T A B the metal tape is provided with at least one row (preferably two) of indexing and transport locator holes. A series of individual windows are formed in the tape to align with the locator holes.

Each individual window includes a central array designed to align a bonding pad pattern on a particular semiconductor device, such as an IC chip or other electronic device, inwardly from the edge of the individual window. It has a metal finger pattern that extends to . The tape is passed through an automated machine that bonds the tape fingers to the IC chips that are then to be attached to the tape, preferably by the TC Gang bonding method.

The IC chip with the metal fingers attached is then cut from the tape and bonded to a second structure for further packaging such as direct mounting onto a printed wiring board or dual in-line packaging (DIP).
or other housing. This latter method allows the fingers with the chip frame attached to be mounted on a more substantial lead frame using a lead array that can ultimately be plugged into a DIP socket or mounted into appropriate holes in a printed wiring board. It usually involves a process of

As previously noted, the assembly tape first passes through an automated machine that bonds the IC chips to each of the tape liner arrays. This is called inner lead fist bonding (ILB) formation. In this work, a thermode (tt+crmode) is used to connect the inner edge of the metal tape finger and the tape finger to the TC.
Pressure is applied to the bonding pads on the chip, as if performing a gang bond. For this operation, the tape is attached to a tape guide that holds the tape in a controlled spatial position.
Pass through the bottom of the shoe. This shoe is shaped so that the tape flexes as it passes through the machine. Such deflection acts to displace elements within the tape finger array and deflect the bonded chip from its intended path. If a bonded chip is deflected, it may come into contact with other unbonded chips placed in the machine and cause rupture. In fully automated equipment, image processing methods are used to determine the finger pattern and align it with the semiconductor device bonding pads. If one lead is bent, its optical reflection may change and image processing may become inaccurate. Automated equipment involves the possibility of confusing bent leads with missing fingers and rejecting the assembly tape.

PRIOR ART In FIG. 1, segment 10 represents a portion of an assembly tape of the type used in the prior art. Locator holes 11 form a row of holes extending along both edges of the tape. These holes are indexed to the finger pattern. One finger pattern is shown extending within the so-called individual window formed by the laterally extending dam bars 12 and tape side rails 13.

The IC chip 14, whose annulus is shown in dash-dotted lines, will be bonded to the inner extension of the finger 15 whose bonding pads extend in a cantilevered manner into the individual window.

First, the chip 14 is attached to tape by an ILB operation. The chip and attached leads are then cut from the tape along dash-dotted lines 16. The outer extensions of the bonded fingers are then attached to the second structure to facilitate chip packaging. One known method is to attach the metal fingers to the metal
It consists of tracing head bonding. The immediate areas of the chip and the wiring board are then coated with a nodule of plastic compound. Another well-known method is to bond metal fingers to a larger substantial lead frame. A plastic molding compound is then formed around the lead frame to create the well-known plastic DIP. The leads within the large lead frame form pin elements that protrude from the molded plastic to create the appropriate connections.

FIG. 2 is a simplified diagram showing the elements of an ILB machine.

In this machine, the processed silicon wafer is mounted on a support plate 18 (usually glass or ceramic) with heat release cement 19. While the wafer is attached to a support plate, it is diced into chips by a saw. This leaves an array of IC chips 20 adhered to plate 18. The ILB machine includes means (not shown) for raising and lowering the plate 18 and indexing it in the X and Y directions. ILB machine has tape 10
Tape guide with positioning channel for storing
A shoe 21 is provided. A hole 22 in the central portion of the shoe 21 is arranged to house a thermode 23 having a bonding surface 24 designed to span between the inner edges of the finger pattern in the tape 10.

Typically, the tape guide shoe 21 has approach and exit reaches that form an angle of approximately 30 degrees with respect to the horizontally aligned central bonding location. The ILB machine also includes a tape transport indexing take-off and supply reel mechanism (not shown). During operation, the machine advances the tape so that the finger pattern is placed precisely under the hole 22. Thereafter, the IC chip mounted on the plate 18 is raised to the bonding position just below the tape guide shoe 21.
It is indexed into position relative to the finger and plate 18. After that, the heated thermode 23
It is lowered and pressed against the tape with sufficient pressure and heat to gang bond the metal fingers to the chip bonding pads. As the thermode is heated for TC bonding, the chip is heated to move it away from element 19 on plate 18.

After that, the thermode 27 rises and the plate 18 falls,
The tape can be advanced to bring the new finger pattern into position and index the new tape section into position.

If desired, an optical monitor (not shown) can be incorporated into the machine to allow observation of the indexing process. Furthermore, if necessary, the tape 10 can be attached to the plate 18.
Automatic optical positioning could also be added.

It can be seen from FIG. 2 that tape 10 must flex as it traverses tape guide shoe 21 as it passes through the ILB machine.

When the tape enters the bonding position from the left, the tape fingers will tend to bend downwardly toward the plate 18. Referring to FIG.
The dam club bar 121 will have a tendency to distort the attached fingers.

This condition can be facilitated by making the dam bar very wide. However, this wastes valuable tape area that could be better used to increase finger pattern density. In other words, it is desirable to make the dam bar 12 as narrow as possible.

Another condition exists for tape exit from the bonding area. - When the tape fingers are bonded to the IC chip, the chip becomes part of the tape. This means that the chip stiffens the tape after bonding.

Therefore, the tape product leaving the bonding area is
It will be considerably stiffer than the incoming product. As a result, tape exiting the bonding area will tend to be unable to follow the tape guide shoe. This causes the tape to form a loop to the right of the bonding location, causing the tape to form a loop around the just-attached chip 2'.
will be placed downward from its expected position. It can be seen that the chips thus displaced come into contact with other chips on the support plate 18. It is important to avoid this condition as it can damage either the bonded chip or the mounted chip (or both). The tape flexibility provided by the present invention solves both of the above problems.

A preferred embodiment of the invention relates to a so-called bump tape in which the metal fingers in the tape pattern are provided with bumps at their ends where they are bonded to IC pads. The present invention is also useful in traditional tape assembly systems where flat metal fingers are bonded to metal bumps formed on IC bonding pads.

Similarly, although a single layer metal tape format is preferred, the present invention can be used on two or three layer assembly tapes.

The tape of FIG. 1 is typically fabricated using a double-sided photolithographic metal etching process. First, both sides of the metal are coated with photoresist. A mask is then used to expose both sides to different light patterns. The side shown in Figure 1 represents the finger pattern. Typically, the locator holes 11 are created at the same time as the fingers are created, so that the exposure mask automatically provides indexed locator holes. The opposite side of the tape is exposed with a pattern of light that leaves resist across the tips of the fingers, but not adjacent portions of the fingers. The tape is then etched on both sides in a step that etches the tape slightly past the halfway mark. Etching both sides will completely remove the metal. This etching creates a raised or bumped area at the tip of the refinger where the finger is thinner in an area adjacent to the tip. This bump allows TC bonding of the tape fingers to common IC chip bonding pads. During TC bonding, the bumps on the fingers may collapse, creating unevenness in the tape or bonding pad.
A reliable gang bonding operation will bond all of the fingers in the pattern at the same time.

Problems and Objects to be Solved by the Invention The object of the invention is to considerably increase the flexibility of the assembly tape.

It is a further object of the invention to isolate successive finger patterns in the assembly tape so that sagging of the tape does not cause deformation of adjacent finger patterns.

It is a further object of the present invention to increase the flexibility of the tape so that it conforms to the shape of the guide shoe by mechanically isolating adjacent finger patterns of the assembly tape.

SUMMARY OF THE INVENTION One or more objects and other objects are achieved in an assembly tape. The tape includes at least one, and preferably two, rows of locator holes extending along the tape edge. Successive finger patterns are separated by narrow transverse sections called dam bars. The dam bar forms the lateral boundary of the individual window into which the finger pattern extends. The longitudinal boundaries are created by side rails extending along the tape and having locator holes. The drive sprocket includes teeth that extend into the locator hole for indexing and transporting the tape. The inner ends of the tape fingers are TC gang bonded to mated bonding pads on the IC chip in an ILB operation where the tape passes under a guide shoe. The tape is made flexible by incorporating hinges into its structure. Form a slot across the dam bar to connect adjacent fingers.
Ensure that patterns are mechanically isolated from each other. In the preferred embodiment, the slot extends to terminate at a line along the inner portion of the locator hole. As a further part of the preferred embodiment, the hinge action extends over a reduced-thickness cross-sectional slot extending across that portion of the tape to the outer edge of the locator hole. This leaves a full thickness section of tape extending from the outer edge of the locator hole to the edge of the tape. This reduced thickness rail portion provides significant strength to the tape to resist shearing motion of the side rails. This reduces compressive stress within the tape as it flexes under the guide shoe. As a result, the tape will closely follow the shape of the guide shoe when it is indexed by the ILB machine. The presence of the slot ensures that the tape fingers are not deflected when the tape flexes. The overall flexibility of the tape prevents bonded chips from touching other unbonded chips in the ILB machine after chip bonding.

EXAMPLE FIG. 3 is a front view of a tape segment similar to FIG. 1, detailing the hinge portion according to the invention. Tape section 20 includes conventional locator holes 11 in side rails 13, dam bars 12, and fingers 15 that extend into the individual windows. Each dam bar 12 is traversed by a slot 21 that extends to a position defined by the inner reach of the locator hole 11.

A reduced thickness portion 22 extends beyond the slot to the outer reach of the locator hole 11. A reduced thickness portion 22 is etched into the tape from the side that is made wider than the slot 21 and defines a tape finger pattern. As previously discussed, the tape has a finger pattern side (shown in FIGS. 1 and 3) and a bump side within which tape bonding bumps are fabricated. This latter side is the side facing away in FIGS. 1 and 3. In the tape production process, Figures 1 and 3
The in-plane etched pattern depicted in the figure will have slots 12 and areas of reduced thickness 22. The bump side of the tape will include etchings of slots 21. The slot thus extends completely through the thickness of the tape, while region 22 extends slightly beyond the middle of the tape.

It can be seen that the slots 21 mechanically isolate adjacent finger patterns. When the tape is flexed prior to chip attachment, no distortion of fingers 15 is observed. They will be located in the initial plane of the tape as it flexes. After the chip is attached to the tape at the ILB, the resulting stiffness of the tape does not significantly reduce the flexibility of the tape and the tape can easily follow its path over the guide shoe.

The reduced thickness region 22 increases the tape deflection at the side rail 13 portion. Because they are etched into the finger pattern side of the tape, they will act to reduce tape flexing effects that tend to place the metal surface in compression. This makes it easier for the tape to sag as it traverses the tape guide shoes in the ILB machine. Region 22 also provides considerable tape strength to resist shearing motion between side rails 13.

As noted with respect to FIG. 1, after ILB the tape finger 15 is cut from the tape at a point located just inside the individual window. This is usually accomplished by a punch and die combination, which must be maintained in sharp conditions and well-controlled relationships. Because the punches are used repeatedly, they become abrasive and therefore occasionally need to be sharpened to produce a clean separation. One great advantage of hinge tape is that it is useful in indicating when the tear-off punch needs to be sharpened.

To do this, inspect the tape scrap as it leaves the cutting operation.

If the punch is dull, the cutting operation will tear and deform the tape material within the dam bar.

The presence of slot 21 results in a very thin dam bar remainder. If the cut is made clean, the rest of the dam bar will be free of distortion. However, if the cutout punch is not sharp enough, the rest of the dam bar will become distorted.

Although FIG. 3 shows an embodiment of the invention, other configurations may be used. For example, region 22 can be made to have the same width as slot 21. Similarly, region 22 could be completely etched over the entire tape rather than being partially etched. The slots 21 could be such that they terminate just across the finger patterns rather than extending to the inner edges of the holes 11 as shown. The essential characteristics are
The objective is to mechanically isolate adjacent finger patterns from each other as the tape flexes while maintaining sufficient resistance to side rail shearing motion.

FIG. 4 shows an alternative form of the invention. In this case dumb bar 1
2 is traversed by a series of slots 31. These slots collectively act to form the equivalent of a transverse slot in a dam bar. Therefore, the slot 31 is the third
This is the equivalent of slot 21 in the figure.

The invention has been described to enable any person skilled in the art to practice the invention without resorting to further invention. Upon reading the foregoing description, alternatives and equivalents will be apparent to such skilled persons within the spirit and spirit of the invention.

Accordingly, it is intended that the scope of the invention be limited only by the claims that follow.

[Brief explanation of drawings]

Figure 1 is a front view of a tape segment showing a conventional type of bonding tape. Figure 2 is a schematic diagram showing a part of an ILB machine. Figure 3 is a front view of a hinge tape segment with a slot that increases deflection. FIG. 4 is a front view of a segment of hinge tape showing an alternative form. 10... Tape segment 11... Locator hole 13... Side rail 12... Dam bar 14... IC chip 15... Finger 1
8...Support plate 20...Tape portion 2
L 31...Slot 22...Reduced thickness area (4 people in addition)) Procedural amendment (method) Showa/;

Claims (1)

[Scope of Claims] 1. A row of indexing and transport locator holes extending along at least one edge, and indexing to the locator holes spaced apart along the length of the tape. an assembly tape having a plurality of independent metal finger patterns, the assembly tape having a plurality of independent metal finger patterns;
an array of fingers each extending inwardly in a cantilevered manner from the edge of the individual window to form an array aligned with a bonding pad pattern on the electronic device to be bonded to the tape; an assembly tape comprising: said independent patterns separated from each other by dam bars extending laterally across said tape and serving to define transverse edges of said individual windows; a pattern is formed in the tape and extends across the dam bar and across the tape to mechanically isolate the finger patterns in adjacent individual windows from each other and increase deflection of the tape; Hinge tape featuring 2. The hinge according to claim 1, wherein the slot pattern is composed of a plurality of independent slots formed in a row creating the equivalent of a single transverse slot. tape. 3. The flexibility of the tape in the dam bar region is substantially improved by having a region in the side rail of reduced thickness that extends in alignment with the slot and spans the locator hole. The hinge tape according to claim 1, characterized in that: 4. The hinge tape of claim 3, wherein said area of reduced thickness is substantially wider than said slot. 5. A first side of the tape photolithographically etched to create the finger pattern; and a second side further etched to define the fingers and provide bonding bumps at inwardly extending ends of the fingers. and etched into the first surface of the tape,
4. A hinge tape as claimed in claim 3, characterized in that it has a region of reduced thickness. 6. A method of producing an assembly tape used for tape assembly bonding metal fingers to an electronic device, each pattern terminating in an array registering a pattern of bonding pads associated with said electronic device. etching the tape to create a series of metal finger patterns with inwardly extending portions; and etching the tape between adjacent metal finger patterns to increase the flexibility of the tape. etching in the region; 7. The method of claim 6, wherein said step of etching includes slots located in regions between said adjacent finger patterns. 8. The tape comprises locator holes used for indexing and transporting the tape in an assembly machine, and the slot extends across the tape and spans the area between the inner ends of the locator holes. The method according to claim 7. 9. The slot further comprises a slot extension region of reduced metal thickness, the extension region being wider than the slot and extending across the tape and spanning the locator hole. The method described in paragraph 8. 10. The method of claim 6, wherein said step of etching includes a series of slots extending across the lateral dimension of said tape in regions between adjacent finger patterns. .